In the semiconductor manufacturing process, a wafer having been previously processed to form integrated circuits therein and/or thereon is thinned. Thinning is performed while the wafer is bonded (temporary bonding) to a transparent (to light) supporting substrate by a joining layer. Further, in order to make the thinned wafer easily separate from the supporting substrate, a photothermal conversion layer that is converted by the energy of visible light is provided between the wafer and the supporting substrate. Then, after thinning the wafer, by irradiating the photothermal conversion layer with visible light from the supporting substrate side of the stack, the properties of the photo thermal conversion layer are changed, allowing separation of the wafer from the supporting substrate.
In the above method, however, the material of the supporting substrate is limited to a transparent material, such as glass. Therefore, the degree of freedom in selecting the material of the supporting substrate is desired to be increased.